I have a sewer gas in my small bath room on other side of wall is my washer and dryer,I have had new seals put under the toilet and checked the sink trapped which is working OK,I have found out for sure the only time the smell occurs is when you use the dryer and the smell is only in the small bath room not the utility room,the dryer is vented straight out the wall,has anyone had this problem an how did you solve it
I have a maytag dryer

It sounds like you have negative pressure where the dryer is located. You need a fresh air vent from outside to supply air into the laundry room. Air is bubbling through the traps when you run the dryer. This is a dangerous situation and can cause a fire or explosion of methane gas. Run a 4 inch line from outside either through the wall or through the ceiling to equal out the pressure.

It sounds like you have negative pressure where the dryer is located. You need a fresh air vent from outside to supply air into the laundry room. Air is bubbling through the traps when you run the dryer. This is a dangerous situation and can cause a fire or explosion of methane gas. Run a 4 inch line from outside either through the wall or through the ceiling to equal out the pressure.

The dryer is vented out side and the doors where the dryer is setting has a inch gap under them

That does not matter. It's the whole house that must be tight. Try opening a window to see if it does it then, especially if the laundry room has a window in it. The dryer has to be pulling the gas out of the sewer some way, otherwise you have a dried up trap on something like a floor drain, and even then the dryer still has to draw the gas out of the drain. A dryer moves a lot of air to dry clothes and must be replaced somehow. You are lucky you are not using a gas dryer or you would have carbon monoxide poisoning. They need even more fresh air.

That does not matter. It's the whole house that must be tight. Try opening a window to see if it does it then, especially if the laundry room has a window in it. The dryer has to be pulling the gas out of the sewer some way, otherwise you have a dried up trap on something like a floor drain, and even then the dryer still has to draw the gas out of the drain. A dryer moves a lot of air to dry clothes and must be replaced somehow. You are lucky you are not using a gas dryer or you would have carbon monoxide poisoning. They need even more fresh air.

I've had a plumber out three times but I'm getting different tomorrow,for some reason the one I,vebeen using seems like he doesn't want to go into the wall and I personally think the roof vent that goes through the roof and comes down inside the wall where the small rest room is I think it has a small leak and when air gets to it then it reall makes the smell bad,the plumber said no that it would smell all the time but I don't buy that.what do you think?

It's a good possibility that there is a leak from that vent. The dryer is drawing the gas in, however.